Piezoelectric crystal holder



El Q1 INVENTOR R s BAILEY ,3 6 PIEZOELEbTRIC CRYSTAL HO LDER Filed April 20, 1942 RICHARD 5 BAILEY 951% Q. W ATTORNE Feb. 15, 1944.

Patented Feb. 1944 7 2,341,683 PIEZOELECTRIC CRYSTi iL HOLDER Richard S. Bailey, Baltimore, Md., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation 01' Delaware Application April 20, 1942, Serial No. 439,671

6 Claims.

This invention relates to the mounting of piezoelectric crystals and more particularly to a crystal holder of improved appearance and enhanced utility.

As is well known, the primary use of piezoelectric quartz crystals is for the control of the frequency of transmitters requiring a high order of stability. In such transmitters, the operating frequency can usually only be changed by inserting a new crystal itno the crystal oscillator circuit, and during operation, any change required is generally made by the adjustment of a selector switch which inserts a selected crystal Figure 2 is a view in perspective of the completed holder with the crystal in place, together with a suitable clip mounting assembly.

Referring to Figure 1, the crystal I is provided y with the conductive coatings 2 and I on either side. At its left end, the crystal I is held by the the operating base for the aircraft; and this latter change requires the physical insertion of new crystals or crystal assemblies into suitable receptacles in the equipment. Among the previously available holders, those which may be readily interchanged without unsoldering or unscrewing connections, as by merely snapping into place have been excessively bulky, and those of minlspected without removal from said assembly.

The above objects and advantages of the invention are accomplished by mounting a crystal provided with metallic films on two sides so that the crystal is held by two spring clamps, each clamp being secured to a cylindrically shaped metallic end-cap one of which, in turn, fits over each end of a transparent cylindrica1 enclosure. Each of the clamps mentioned makes contact to only one of the conducting films, and connection to the crystal controlled circuit is established through the metallic end-caps.

Other objects and advantages of the invention will in part be disclosed and in part be obvious when the following specification is read in conjunction with the drawing in which:

Figure 1 is a side view of the completed holder, with the crystal in place.

spring clamp 4 which is of conducting material and makes contact with the conductive film 2, conductive film 3 being removed in the region contacted by the clamp 4. At its right end, the crystal I is mm by the spring clamp 5, also oi! conducting material which makes contact with the conductive film 3, conductive film 2 being removed in the region contacted by the clamp 8. The clamp 4 is carried on a cylindrical mounting support 6, of which a portion I is reduced in diameter, The reduced portion I of the mounting support extends through the aperture I in the end-cap 9 and the projecting segment is peened over as at ID to secure the clamp assembly in the end-cap. Where a hermetic seal is desired, the reduced portion I may be sweated in place, thus eliminating the need for the peening operation. The spring clamp 5 is similarlymounted to the end-cap I I. The enclosure surrounding the crystal I is completed by th cylindrically shaped glass or transparent plastic container I2, the endcaps 9 and II being slipped over the opposite ends of the cylinder thus defined. The end-caps may be cemented or otherwise suitably secured to the container of body I2 to maintain them in place, the care and method used in this operation being dependent on the excellence of seal required. Hermetically sealed containers may be evacuated or filled with any desired fluid or gas.

The perspective view of Figure 2 shows the neat and attractive appearance of the completely assembled crysta1 and holder, with the nd caps 9 and I I in place at opposite ends of the cylindrical enclosure I2 and the spring clamps 5 and 4 (not shown) supporting the crystal I and making contact to the conductive coatings 3 and 2 respectively. This view shows the crystal and 'holder The end-caps 9 and II are at once the means of establishing electrical connection to the crystal electrodes and supporting the assembly. The necessary electrical connections to the crystal controlled circuit are preferably brought out to a pair of spaced metallic spring clips in a mounting of the general type Just described, and the :completed assembly is then snapped into place When in the spring clips in the usual manner. the necessity arises for changing the operating frequency of the crystal controlled equipment, it

is necessary merely to snap the old assembly out and insert the new one in its place, the entire operation consuming but a few seconds. At any time that it may be deemed advisable the crystal element may be visually inspected to determine whether it is cracked or broken without removing the holder and crystal assembly from the supporting clips and without removing the crystal from the holder itself. It is readily observed that the entire volume occupied by the crystal and holder is far less than that of other apparatus for the same purpose in present use.

While I have described theuse of a transparent enclosure, it is evident that the mechanical advantage of rapid interchangeability will be retained upon the substitution oian opaque sub-' stance for this purpose, only the advantage of facile visual inspection being lost. The conductive films on the surface of the crystal may be found thereon by sputtering, or plating, or may consist simply of metallic foil cemented in place. The tubular crystal enclosure need not necessarily be of circular cross section, but may exducting electrodes, a tubular enclosure of insu-,

lating material surrounding said plate, a conducting end-cap at each end of said tubular enclosure, and clamping means carried by each of said end-caps, said plate being secured by said clamping means, and each of said clamping and spring clamping means secured to each of said end-caps, said plate being mounted at opposite ends in said clamping means, said clamping means also making electrical contact with one of said conducting electrodes.

3. In combination with a plate of piezo-electric material having two operatively associated conducting electrodes, a tubular enclosure of insulating material surrounding said plate, a cylindrically shaped conducting end-cap slipped over each end of said tubular enclosure, and spring clamping means secured to each of said end-caps, said plate being mounted at opposite ends in said clamping means, said clamping means also making electrical contact with one of said conducting electrodes.

i. In combination with a plate of piezo-electric material having two operatively associated conducting electrodes, a tubular enclosure of trans- ,parent insulating material surrounding'said plate.

a conducting end-cap at each end of said tubular enclosure, and clamping meanscarried by each of said end-caps, said plate being secured by said clamping means, and each of said clamping means also making electrical contact with one of said conducting electrodes.

5. In combination with a plate of piezo-electric material having two operatively associated conducting electrodes, a tubular enclosure -of insulating material surroundingsaid plate, the axis of said tubular enclosure being substantially parallel with the plane of said plate, a conducting 'end-cap at each end of said tubular enclosure,

means also making electrical contact with one of 7 and clamping means carried by each of said endcaps'. said plate being secured by said clamping means, and each of said clamping means also making electrical contact with one of said con ducting electrodes.

6." In combtion with a plate of piezo-electric material having two dperatively associated conducting electrodes, a tubular enclosure of transparent insulating material surrounding said plate, the axis or said tubular enclosure bein sutantially parallel with the plane of said plate; a cylindrically shaped end-cap having a central aperture slipped over each of said tubular enclosure and cemented in place, and a springclamp mounted in each or said central apertures of said end-caps, said plate being held in place between the clamping members of said spring clamp, each of said clamping members also making electrical contact with one of said conducting electrodes.

. RICHARD S. BAILEY. 

